Hamburg 2009 – scientific programme
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MS: Fachverband Massenspektrometrie
MS 5: AMS-Developments
MS 5.2: Talk
Tuesday, March 3, 2009, 14:15–14:30, VMP 8 R05
Additional Isobar suppression in AMS using selective laser photodetachment — •Oliver Forstner1, Pontus Andersson2, Christoph Diehl3, Robin Golser1, Dag Hanstorp2, Walter Kutschera1, Anton Lindahl2, Christof Vockenhuber4, and Klaus Wendt3 — 1Universität Wien, Wien, Austria — 2Göteborg University, Gothenburg, Sweden — 3Johannes Gutenberg Universität, Mainz, Germany — 4ETH Zurich, Switzerland
We are investigating the possibility to use laser photodetachment of negative ions as an isobar-selective filter in accelerator mass spectrometry (AMS). The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at 3-MV AMS facilities.
The present detection limit for measuring the isotope ratio 182Hf/Hf at VERA is 1x10−11. The limiting factor is the strong background of the stable isobar 182W. Currently this background is reduced using suitable molecular ions in the injection stage of VERA. Test experiments have been carried out in a low-energy, negative-ion-beam setup at Göteborg University, where a pulsed tunable laser beam is used to measure the absolute photodetachment cross section of negative fluoride ions from W and Hf. The most promising of the investigated molecular ions is HfF5−, which shows a high production yield from the ion source and a negligible photodetachment cross section at the tripled fundamental wavelength of a Nd:YAG laser. At this wavelength an electron detachment of WF5− ions is clearly observed and the detachment cross section rises with increasing photon energy.